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Juveniles of these species in winter show a stronger 

 association with the bottom than in summer. It was 

 postulated that such winter behavior affords protection 

 against predation and displacement. Movement away from 

 cover or the emergence from the bottom in summer allows the 

 juveniles to effectively feed during the season when 

 drifting food is more abundant and the higher metabolic rate 

 allows more food to be used. 



Some salmonids enter the substrate in winter. Chapman and 

 Bjornn (1958) reported that young steelhead and Chinook 

 salmon, anadromous species not found in Montana, often 

 overwinter in the stream substrate under large stones, rocks 

 and debris. Hanson (1977) documented this behavior for 

 resident cutthroat, which entered the substrate when winter 

 water temperatures decreased to 4.4C or less. This 

 behavior was considered an adaption to avoid predators, 

 physical damage by ice and unnecessary energy expenditures 

 (Chapman and Bjornn, 1968). 



Habitat selection by salmonids can be different in winter 

 than during warmer periods, a conclusion substantiated by 

 the work of the above authors. There is, however, no 

 general concensus concerning the makeup of the preferred 

 winter habitats. Many factors, including the species and 

 life stages of fish and the presence or absence of surface 

 ice and other forms of cover, appear to influence winter 



